The invention pertains to the art of handling and moving bulky objects. In the fields of manufacturing, warehousing, et cetera, it is often necessary to repetitively move large numbers of identical objects. In many cases such items are large, bulky and heavy. In manufacturing, often the form of motion required includes rolling to provide access to facilitate assembly and testing of variously located parts of a workpiece. Frequently such objects must be moved by hand. This invention significantly reduces the work required to move such objects by reducing the amount of energy expended.
Methods developed in the past commonly include various types of hand trucks, self dumping hoppers and pivoted or leveraged machines. The present invention significantly and surprisingly reduces work without recourse to complex and expensive auxiliary machines.
This invention provides a method for rolling heavy, bulky workpieces from one point to another with a minimum expenditure of mechanical work. This invention also provides a method for rapidly handling large numbers of identical heavy, bulky workpieces in sequence.
These advantages of the invention are provided by a ramp having a surface contoured to correspond with the contour of the workpiece to be moved as it rotates about its center of gravity (CG) which remains at a constant elevation as it horizontally translates along the ramp. The simplest example of such a ramp is a flat horizontal plane in conjunction with a circular object such as a wheel or a ball having a geometrically central CG. However, many objects do not meet the criteria of symmetry and concentricity of a wheel. Thus, a ramp constructed according to the present invention facilitates rolling an aconcentric, asymmetric workpiece without changing the elevation of the CG of that workpiece, and a method for designing the contour of that ramp.
One of the simplest and most common shapes which must be handled is the rectangular box. Yet, in order to determine the contour of a ramp according to this invention, a series of complex analytical steps must be accomplished. Even for the case, of the rectangular box, where the rolling contour of the workpiece comprises straight lines, the equation for the profile of the ramp surface is complex. In cases where said rolling contour is curvilinear, an equation describing the corresponding ramp surface may be determined by the same series of analytical steps.
A solution can be determined by competent designers for any workpiece which does not include an unrounded acute angle corner through which it must be rolled. When acute angle corners are encountered, the extent of rounding required to accommodate this invention without binding depends on the sharpness of the angle and the overall contour of the rolling workpiece. Therefore, the extent of corner rounding will vary from case to case and must be determined by the designer.
Another important feature of the invention is the contact material between the rolling workpiece and the ramp. If significant slippage were to occur between the workpiece and the ramp, the elevation of the CG and the geometric relationship between the contact surfaces would both change. Therefore, it is extremely important that such slippage be prevented.